I take these myself and I read a study from Canada about Vit. D3 and breast cancer so I sent my daughter a bottle as she has breast cancer and asked her to take 3 to 5 a day and she tells me that she is feeling better but has had no scans as of yet to determine any effect.I like being able to buy the 10,000 IU instead of taking so many.

I've been using this for just over 6 months now.
What I have noticed is that my skin appears to be much smoother than before (though I observed this approximately 2 months ago).
Other than that... my partner was on it for the last month or so.
I've been giving him roughly 2 capsules per day (along with Vitamin K2 as MK-7).
He noticed that he doesn't get tired as often as before, and that his skin also appears to be more smooth than before (I gave him 10 capsules for about 8 days in a row because I read that each 10 000 IU equals 1 ng/mL... so I wanted to raise his levels quite fast).
Right now I've lowered his dosage to 10 000 IU daily, although I think I can reduce it further to 40 000 IU per week for maintenance purposes.
My dose is currently at maintenance levels (4 capsules per week) because I've been on this for the last 6 months already.
We hadn't had a chance to test our Vitamin D3 levels yet at all... but both of us are not exactly in the sun to begin with, and since we are in Scotland, the sun here appears in full force on a rare basis.
I actually had a pretty good idea that both of us were quite deficient in D3 (especially me).
Plus, I also noticed that I've been feeling healthier overall since taking it.
I think this product is great... but I wouldn't mind iHerb offering Vitamin K2 as MK7 (100 mcg) along with D3 10 000 IU both in 1 capsule.
Packing these potencies and forms together would be pretty great and likely lower the overall costs in the long term.